PROJECT SUMMARY Small non-coding RNAs, in particular microRNAs, play significant roles in regulation of various biological processes and their dysregulation leads to disorders. Recently, their role in cell-cell and cross-species communications has also been revealed. Research has shown that a subset of stable microRNAs is present in high abundance in blood which may affect other tissues or microorganisms exposed to them. In this innovative project, we aim to explore the potential role of human blood circulating microRNAs taken up by mosquitoes in regulating expression of genes in the mosquitoes and their effect on replication of viruses that they transmit. As a model, we will use Aedes aegypti, a notorious vector of several arboviruses, and dengue virus as the second most important vector-borne pathogen. Our preliminary data shows that blood-derived microRNAs are stable in mosquitoes for hours, successfully pass the mosquito midgut into other tissues in the body cavity and importantly occur in biologically abundant numbers. In addition, our preliminary results show that at least one of the human blood microRNAs alter mosquito genes that are involved in mosquito immunity and reproduction. We hypothesize that (i) circulating human blood-derived miRNAs obtained through blood feeding are absorbed through the mosquito midgut and translocated into mosquito tissues, and (ii) the exchanged miRNAs play roles in mosquito biology and affect replication of viruses they transmit. To address these hypotheses, we aim 1) to analyze human blood miRNAs in Ae. aegypti biology, 2) to identify the target genes of blood miRNAs in Ae. aegypti and their effect on mosquito biology, and 3) determine the effect of inhibition of human blood miRNAs on mosquito-virus interactions. We anticipate that the outcomes will advance our understanding of the molecular events following blood uptake by mosquitoes, and build-up of essential knowledge in identification of potential target molecules for interfering in mosquito reproduction or virus replication.